没有参数的Moq ReturnAsync()

问题描述

我使用起订量.我模拟了一个类，该类具有如下所示的方法:

I use Moq. I have mocked a class which has method that looks like following:

public async Task DoSomething()
{
    // do something...
}

我将其设置如下:

SomeMock.Setup(x => x.DoSomething())
                .Callback(() => ... ))
                .Returns(Task.FromResult(default(int)));

我不喜欢最后一行:.Returns(Task.FromResult(default(int))).有没有一种方法可以以更优雅的方式设置异步返回.我知道有一个方法ReturnsAsync()，但是它有一个参数.我的方法只返回Task，所以我没有ReturnsAsync()的参数.

I don't like last line: .Returns(Task.FromResult(default(int))). Is there a way to setup async return in more elegant way. I know there is a method ReturnsAsync() but it has a parameter. My method returns just Task so I don't have a parameter for ReturnsAsync().

推荐答案

尝试执行以下操作:

someMock.Setup(x => x.DoSomething())
   .Callback(() => {})
   .Returns(Task.CompletedTask);

请注意，Task.CompletedTask仅存在于.NET 4.6(最近发布)中或更高版本中.您可以在此 StackOverflow答案中找到更多信息.

Note that Task.CompletedTask only exists in .NET 4.6 (which was released very recently) or newer. You can find more information in this StackOverflow answer.

ReturnsAsync用于异步返回值时.当您仅返回Task时，您实际上根本没有返回任何异步值，因此ReturnsAsync并没有真正适合"此处.

ReturnsAsync is for use when you are returning a value asynchronously. When you are returning just a Task, you are not actually returning any asynchronous value at all, so ReturnsAsync doesn't really 'fit' here.

如果这不符合您的需求，很遗憾，您将不得不使用Task.FromResult().据我所知，这实际上是创建完成的"任务的唯一方法-除了new Task(() => {})之外的 new Task(() => {})导致死锁.使用Task.Run(() => {}).

If this doesn't suit your needs, you will have to use Task.FromResult(), unfortunately. As far as I know this is really the only way to create a 'completed' task - new Task(() => {}) causes a deadlock. Use Task.Run(() => {}).

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